During the coming year the clinical studies will continue on the selection of patients with chronic ventilatory insufficiency for diaphragm pacing. In addition, particular emphasis will be on the evaluation of diaphragm pacing in patients with, 1) quadriplegia, and 2) upper airway obstruction and Leigh's disease complicated by central alveolar hypoventilation. Further, a study of the loss of hypoxic drive in patients with ventilatory insufficiency requiring diaphragm pacing will be made. A registry of all patients with diaphragm pacemakers will be maintained. In the electronics laboratory a re-evaluation of the design and function of the diaphragm pacemaker and its components, the transmitter, radio receiver and electrode assembly, will be made to achieve present state of the art performance. In the animal laboratory a detailed study of tissue reaction to several newly designed electrodes and waveforms will be tested. A quantitative study of tissue perfusion by heat loss calorimetry will be expanded. Bibliographic references: Hogan JF, Holcomb WG, Glenn WWL: Design of a radiofrequency pulse duration modulated system for phrenic pacing. Proceed San Diego Biomed Symp 14:329, 1975. Glenn WWL, Liebow AA, Lindskog GE: Thoracic and Cardiovascular Surgery with Related Pathology. Appleton Century Crofts, New York, 1975.